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Diverse and tissue-enriched small RNAs in the plant pathogenic fungus, Magnaporthe oryzae.

ABSTRACT: BACKGROUND: Emerging knowledge of the impact of small RNAs as important cellular regulators has prompted an explosion of small transcriptome sequencing projects. Although significant progress has been made towards small RNA discovery and biogenesis in higher eukaryotes and other model organisms, knowledge in simple eukaryotes such as filamentous fungi remains limited. RESULTS: Here, we used 454 pyrosequencing to present a detailed analysis of the small RNA transcriptome (~ 15 - 40 nucleotides in length) from mycelia and appressoria tissues of the rice blast fungal pathogen, Magnaporthe oryzae. Small RNAs mapped to numerous nuclear and mitochondrial genomic features including repetitive elements, tRNA loci, rRNAs, protein coding genes, snRNAs and intergenic regions. For most elements, small RNAs mapped primarily to the sense strand with the exception of repetitive elements to which small RNAs mapped in the sense and antisense orientation in near equal proportions. Inspection of the small RNAs revealed a preference for U and suppression of C at position 1, particularly for antisense mapping small RNAs. In the mycelia library, small RNAs of the size 18 - 23 nt were enriched for intergenic regions and repetitive elements. Small RNAs mapping to LTR retrotransposons were classified as LTR retrotransposon-siRNAs (LTR-siRNAs). Conversely, the appressoria library had a greater proportion of 28 - 35 nt small RNAs mapping to tRNA loci, and were classified as tRNA-derived RNA fragments (tRFs). LTR-siRNAs and tRFs were independently validated by 3' RACE PCR and northern blots, respectively. CONCLUSIONS: Our findings suggest M. oryzae small RNAs differentially accumulate in vegetative and specialized-infection tissues and may play an active role in genome integrity and regulating growth and development.

SUBMITTER: Nunes CC

PROVIDER: S-EPMC3132168 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Diverse and tissue-enriched small RNAs in the plant pathogenic fungus, Magnaporthe oryzae.

Nunes Cristiano C CC Gowda Malali M Sailsbery Joshua J Xue Minfeng M Chen Feng F Brown Douglas E DE Oh Yeonyee Y Mitchell Thomas K TK Dean Ralph A RA

BMC genomics 20110602

<h4>Background</h4>Emerging knowledge of the impact of small RNAs as important cellular regulators has prompted an explosion of small transcriptome sequencing projects. Although significant progress has been made towards small RNA discovery and biogenesis in higher eukaryotes and other model organisms, knowledge in simple eukaryotes such as filamentous fungi remains limited.<h4>Results</h4>Here, we used 454 pyrosequencing to present a detailed analysis of the small RNA transcriptome (~ 15 - 40 n ...[more]

PMID: 21635781

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Project description:Acetylation and deacetylation of histones are key epigenetic mechanisms for gene regulation in response to environmental stimuli. RPD3 is a well-conserved class I histone deacetylase (HDAC) that is involved in diverse biological processes. Here, we investigated the roles of the Magnaporthe oryzae RPD3 (MoRPD3) gene, an ortholog of Saccharomyces cerevisiae Rpd3, during development and pathogenesis in the model plant-pathogenic fungus Magnaporthe oryzae. We demonstrated that the MoRPD3 gene is able to functionally complement the yeast Rpd3 deletion mutant despite the C-terminal extension of the MoRPD3 protein. MoRPD3 localizes primarily to the nuclei of vegetative hyphae, asexual spores, and invasive hyphae. Deletion of MoRPD3 appears to be lethal. Depletion of MoRPD3 transcripts via gene silencing (MoRPD3kd, where "kd" stands for "knockdown") has opposing effects on asexual and sexual reproduction. Although conidial germination and appressorium formation rates of the mutants were almost comparable to those of the wild type, in-depth analysis revealed that the appressoria of mutants are smaller than those of the wild type. Furthermore, the MoRPD3kd strain shows a significant reduction in pathogenicity, which can be attributed to the delay in appressorium-mediated penetration and impaired invasive growth. Interestingly, MoRPD3 does not regulate potassium transporters, as shown for Rpd3 of S. cerevisiae. However, it functioned in association with the target of rapamycin (TOR) kinase pathway, resulting in the dependency of appressorium formation on hydrophilic surfaces and on TOR's inhibition by MoRPD3. Taken together, our results uncovered distinct and evolutionarily conserved roles of MoRPD3 in regulating fungal reproduction, infection-specific development, and virulence. IMPORTANCE RPD3 is an evolutionarily conserved class I histone deacetylase (HDAC) that plays a pivotal role in diverse cellular processes. In filamentous fungal pathogens, abrogation of the gene encoding RPD3 results in either lethality or severe growth impairment, making subsequent genetic analyses challenging. Magnaporthe oryzae is a causal agent of rice blast disease, which is responsible for significant annual yield losses in rice production. Here, we characterized the RPD3 gene of M. oryzae (MoRPD3) in unprecedented detail using a gene-silencing approach. We provide evidence that MoRPD3 is a bona fide HDAC regulating fungal reproduction and pathogenic development by potentially being involved in the TOR-mediated signaling pathway. To the best of our knowledge, this work is the most comprehensive genetic dissection of RPD3 in filamentous fungal pathogens. Our work extends and deepens our understanding of how an epigenetic factor is implicated in the development and virulence of fungal pathogens of plants.

Dataset Information

Diverse and tissue-enriched small RNAs in the plant pathogenic fungus, Magnaporthe oryzae.

Publications

Diverse and tissue-enriched small RNAs in the plant pathogenic fungus, Magnaporthe oryzae.

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